Pilot signals for synchronization and/or channel estimation

ABSTRACT

The frame words of the preferred embodiment are especially suitable for frame synchronization and/or channel estimation. By adding the autocorrelation and cross-correlation functions of frame words, double maximum values equal in magnitude and opposite polarity at zero and middle shifts are obtained. This property can be used to slot-by-slot, double-check frame synchronization timing, single frame synchronization and/or channel estimation and allows reduction of the synchronization search time. Further, the present invention allows a simpler construction of a correlator circuit for a receiver.

This application is a Continuation of application Ser. No. 09/376,373filed Aug. 18, 1999 now U.S. Pat. No. 6,721,299 which is a ContinuationIn Part of Ser. No. 09/373,703 filed on Aug. 13, 1999 now U.S. Pat. No.6,791,960, which is a Utility filing of Provisional Application60/136,763 filed May 28, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to communication systems, and moreparticularly, cellular communication systems.

2. Background of the Related Art

The use of code division multiple access (CDMA) modulation techniques isone of several techniques for facilitating communications in which alarge number of systems are present. FIG. 1 generally illustrates asystem 10, which uses CDMA modulation techniques in communicationbetween user equipment (UE) 12 a and 12 b, each UE including a cellulartelephone, and base stations (BTS) 14 a and 14 b. A base stationcontroller (BSC) 16 typically includes an interface and processingcircuitry for providing system control to the BTS 14 a, 14 b. The BSC 16controls the routing of telephone calls from the public switchedtelephone network (PSTN) to the appropriate BTS for transmission to theappropriate UE. The BSC 16 also controls the routing of calls from theUEs, via at least one BTS to the PSTN. The BSC 16 may direct callsbetween UEs via the appropriate BTS since UEs do not typicallycommunicate directly with one another. The BSC 16 may be coupled to theBTS 14 a and 14 b by various means including dedicated telephone lines,optical fiber links or by microwave communication links.

The arrows 13 a-13 d define the possible communication links between theBTS 14 a and UEs 12 a and 12 b. The arrows 15 a-15 d define the possiblecommunication links between the BTS 14 ba and UEs 12 a and 12 b. In thereverse channel or uplink (i.e., from UE to BTS), the UE signals isreceived by BTS 14 a and/or BTS 14 b, which, after demodulation andcombining, pass the signal forward to the combining point, typically tothe BSC 16. In the forward channel or downlink (i.e., from BTS to UE),the BTS signals are received by UE 12 a and/or UE 12 b. The above systemis described in U.S. Pat. Nos. 5,101,501; 5,103,459; 5,109,390; and5,416,797, whose entire disclosure is hereby incorporated by referencetherein.

A radio channel is a generally hostile medium in nature. It is ratherdifficult to predict its behavior. Traditionally, the radio channels aremodeled in a statistical way using real propagation measurement data. Ingeneral, the signal fading in a radio environment can be decomposed intoa large-scale path loss component together with a medium-scale slowvarying component having a log-normal distribution, and a small-scalefast varying component with a Rician or Rayleigh distribution, dependingon the presence or absence of the line-of-sight (LOS) situation betweenthe transmitter and the receiver.

FIG. 2 illustrates these three different propagation phenomena. Anextreme variation in the transmission path between the transmitter andreceiver can be found, ranging from direct LOS to severely obstructedpaths due to buildings, mountains, or foliage. The phenomenon ofdecreasing received power with distance due to reflection, diffractionaround structures, and refraction is known as path loss.

As shown, the transmitted signal is reflected by many obstacles betweena transmitter and a receiver, thus creating a multipath channel. Due tothe interference among many multipaths with different time delays, thereceived signal suffers from frequency selective multipath fading. Forexample, when the 2 GHz carrier frequency band is used and a car havinga UE is travelling at a speed of 100 km/h, the maximum Doppler frequencyof fading is 185 Hz. While coherent detection can be used to increaselink capacity, under such fast fading, the channel estimation forcoherent detection is generally very difficult to achieve. Because offading channels, it is hard to obtain a phase reference for the coherentdetection of data modulated signal. Therefore, it is beneficial to havea separate pilot channel.

Typically, a channel estimate for coherent detection is obtained from acommon pilot channel. However, a common pilot channel transmitted withan omnidirectional antenna experiences a different radio channel than atraffic channel signal transmitted through a narrow beam. It has beennoticed that common control channels are often problematic in thedownlink when adaptive antennas are used. The problem can becircumvented by user dedicated pilot symbols, which are used as areference signal for the channel estimation. The dedicated pilot symbolscan either be time or code multiplexed.

FIG. 3 depicts a block diagram of a transmitter and a receiver for timemultiplexed pilot symbols for an improved channel estimation method thatworks satisfactorily under slow-to-fast fading environments. Known pilotsymbols are periodically multiplexed with the sequence of thetransmitted data. The pilot symbols and data symbols following pilotsymbols constitute a slot, as shown in FIG. 3.

Further, in a DS-CDMA transmitter, the information signal is modulatedby a spreading code, and in the receiver, it is correlated with areplica of the same code. Thus, low cross-correlation between thedesired and interfering users is important to suppress the multipleaccess interference. Good autocorrelation properties are required forreliable initial synchronization, since large sidelobes of theautocorrelation function may lead to erroneous code synchronizationdecisions. Furthermore, good autocorrelation properties are important toreliably separate the multipath components.

Since the autocorrelation function of a spreading code should resemble,as much as possible, the autocorrelation function of white Gaussiannoise, the DS code sequences are also called pseudo-noise (PN)sequences. The autocorrelation and cross-correlation functions areconnected in such a way that it is not possible to achieve goodautocorrelation and cross-correlation values simultaneously. This can beintuitively explained by noting that having good autocorrelationproperties is also an indication of good randomness of a sequence.Random codes exhibit worse cross-correlation properties thandeterministic codes.

Such mobile communication system has gone through different stages ofevolution, and various countries used different standards. Firstgeneration mobile systems in the 1980s used analog transmission forspeech services. Advanced Mobile Phone Service (AMPS) in the UnitedStates, Total Access Communication System (TACS) in the United Kingdom,Nordic Mobile Telephones (NMT) in Scandinavia, Nippon Telephone andTelegraph (NTT) in Japan, etc., belonged to the first generation.

Second generation systems using digital transmission were introduced inthe late 1980s. They offer higher spectrum efficiency, better dataservices, and more advanced roaming than the first generation systems.Global System for Mobile Communications (GSM) in Europe, PersonalDigital Cellular (PDC) in Japan, and IS-95 in the United States belongedto the second generation.

Recently, third generation mobile radio networks have been under intenseresearch and discussion and will emerge around the year 2000. In theInternational Telecommunication Union (ITU), the third generationnetworks are called International Mobile Telecommunications—2000(IMT-2000) and in Europe, Universal Mobile Telecommunication System(UMTS). IMT-2000 will provide a multitude of services, includingmultimedia and high bit rate packet data.

Wideband CDMA has emerged as the mainstream air interface solution forthe third generation networks. Wideband CDMA systems are currently beingstandardized by the European Telecommunications Standards Institute(ETSI) of Europe, the Association for Radio Industry and Business (ARIB)of Japan, the TIA Engineering Committees TR45 and TR46 and the T1committee T1P1 of the United states, and the TelecommunicationTechnology Association TTA I and TTA II (renamed Global CDMA I and II,respectively) in Korea. The above description and a background ofvarious systems can be found in WIDEBAND CDMA FOR THIRD GENERATIONMOBILE COMMUNICATIONS by T. Ojanpera et al, published 1998, by ArtechHouse Publishers, whose entire disclosure is hereby incorporated byreference therein.

Recently, ARIB in Japan, ETSI in Europe, T1 in U.S.A., and TTA in Koreahave mapped out a third generation mobile communication system based ona core network and radio access technique of an existing global systemfor mobile communications (GSM) to provide various services includingmultimedia, such as audio, video and data. They have agreed to apartnership study for the presentation of a technical specification onthe evolved next generation mobile communication system and named aproject for the partnership study as a third generation partnershipproject (3GPP).

The 3GPP is classified into three part technical studies. The first partis a 3GPP system structure and service capability based on the 3GPPspecification. The second part is a study of a universal terrestrialradio access network (UTRAN), which is a radio access network (RAN)applying wideband CDMA technique based on a frequency division duplex(FDD) mode, and a TD-CDMA technique based on a time division duplex(TDD) mode. The third part is a study of a core network evolved from asecond generation GSM, which has third generation networkingcapabilities, such as mobility management and global roaming.

Among the technical studies of the 3GPP, the UTRAN study defines andspecifies the transport and physical channels. This technicalspecification, TS S1.11 v1.1.0, was distributed on March of 1999, whoseentire disclosure is hereby incorporated by reference therein. Thephysical channel includes the dedicated physical channels (DPCHs) usedin the uplink and downlink. Each DPCH is generally provided with threelayers, e.g., superframes, radio frames and timeslots. As specified inthe 3GPP radio access network (RAN) standard, a superframe has a maximumframe unit of 720 ms period. In view of the system frame numbers, onesuperframe is composed of seventy-two radio frames. Each radio frame hasa period of 10 ms, and a radio frame includes sixteen timeslots, each ofwhich includes fields with corresponding information bits based on theDPCH.

FIG. 4 illustrates a frame structure of an uplink DPCH based on the 3GPPRAN standard. The uplink DPCH is provided with two types of channels,e.g., a dedicated physical data channel (DPDCH) and a dedicated physicalcontrol channel (DPCCH). The uplink DPDCH is adapted to transport thededicated data and the uplink DPCCH is adapted to transport the controlinformation.

The uplink DPCCH for the transport of the control information includesvarious fields such as a pilot field 21 of N_(pilot) bits, a transmitpower-control (TPC) field 22 of N_(TPC) bits, a feedback information(FBI) field 23 of N_(FBI) bits and an optional transport-combinationindicator (TFCI) field 24 of N_(TFCI) bits. The pilot field 21 includespilot bits N_(pilot) for supporting channel estimation for coherentdetection. The TFCI field 4 supports the simultaneous provision of aplurality of services by the system. The absence of the TFCI field 4 inthe uplink DPCCH signifies that the associated service is a fixed rateservice. The parameter k determines the number of bits per uplinkDPDCH/DPCCH slot. It is related to the spreading factor SF of thephysical channel as SF=256/2^(k). The spreading factor SF may thus rangefrom 256 down to 4.

FIG. 5 is a table showing various information of the uplink DPCCH,wherein channel bit and symbol rates are those just prior to spreading.(At the time of this technical specification, the exact number of bitsof the different uplink DPCCH fields of FIG. 4 (N_(pilot), N_(TPC),N_(FBI), and N_(TFCI)) was not determined.)

FIG. 6 is a table illustrating pilot bit patterns of the uplink DPCCH,and more particularly, 6-bit and 8-bit pilot bit patterns for each slot.In FIG. 6, the non-shaded sequence is used for channel estimation, andshaded sequence can be used as frame synchronization words or sequences.The pilot bits other than frame synchronization word, e.g., channelestimation word, have a value of 1.

For example, in the case where each slot includes six pilot bitsN_(pilot)=6, the sequences formed by slot #1 to slot #16 at bit #1, atbit #2, at bit #4, and at bit #5 are used as the frame synchronizationwords. In the case where each slot is composed of eight pilot bits(N_(pilot)=8), the sequences at bit #1, at bit #3, at bit #5, and at bit#7 are used as the frame synchronization words. In the case where thepilot bits of each sequences slot are either 6 or 8 in number, a totalof four is used as the frame synchronization word. As a result, becauseone radio frame is provided with sixteen timeslots, the number of pilotbits used as the frame synchronization word is 64 bits per frame.

FIG. 7 shows a spreading/scrambling arrangement for the uplink DPCHbased on the 3GPP RAN standard. The arrangement of FIG. 7 is providedfor the execution of a quadrature phase shift keying (QPSK) operationwhere the uplink DPDCH and DPCCH are mapped into I and Q channelbranches, respectively.

The spreading is an operation for switching all symbols through therespective channel branches to a plurality of chips. The I and Q channelbranches are spread respectively at chip rates based on two differentorthogonal variable spreading factors (OVSFs), or channelizing codesC_(D) and C_(C). The OVSF represents the number of chips per symbol oneach channel branch. The spread of two channel branches are summed andthen complex-scrambled by a specific complex scrambling code C_(scramb).The complex-scrambled result is separated into real and imaginary andthen transmitted after being placed on respective carriers.

FIG. 8 illustrates a frame structure of a downlink DPCH based on the3GPP RAN standard. The number of pilot bits (or symbols) in the uplinkDPCH is 6 or 8 because the uplink DPCH is activated at a fixed rate of16 Kbps. However, since the downlink DPCH is activated at a variablerate, it has pilot symbol patterns illustrated in FIG. 9.

With reference to FIG. 8, similar to the uplink DPCH, the downlink DPCHis provided with two types of channels, e.g., a dedicated physical datachannel (DPDCH) and a dedicated physical control channel (DPCCH). In thedownlink DPCH, the downlink DPDCH is adapted to transport the dedicateddata and the downlink DPCCH is adapted to transport the controlinformation. The downlink DPCCH for transporting the control informationis composed of various fields such as a pilot field 27, TPC field 26 andTFCI field 25. The pilot field 27 includes pilot symbols for supportingthe channel estimation for coherent detection.

FIG. 9 is a table illustrating pilot symbol patterns contained in thedownlink DPCCH, which are classified according to different symbol ratesof the downlink DPCCH. For example, in the case where the symbol rate is16, 32, 64 or 128 Kbps, each slot includes four pilot symbols for an Ichannel branch and four pilot symbols for a Q channel branch, totalingeight pilot symbols.

In FIG. 9, the non-shaded sequence is used for channel estimation andshaded sequences can be used as frame synchronization words. Theremaining pilot symbols other than the frame synchronization word (e.g.,channel estimation) have a value of 11. For example, in the case wherethe symbol rate is 16, 32, 64 or 128 Kbps, the sequences, formed bypilot symbols from slot #1 to slot #16, at symbol #1 and at symbol #3are used as the frame synchronization words. Accordingly, because thenumber of pilot symbols used as the frame synchronization words is 4 perslot, 64 pilot symbols are used in each radio frame.

FIG. 10 illustrates a spreading/scrambling arrangement for the downlinkDPCH based on the 3GPP RAN standard. The arrangement of FIG. 10 isprovided for the spreading and scrambling of the downlink DPCH and acommon control physical channel (CCPCH). A QPSK operation is performedwith respect to a pair of symbols of the two channels in such a mannerthat they are serial-to-parallel converted and then mapped into I and Qchannel branches, respectively.

The I and Q channel branches are spread respectively at chip rates basedon two equal channelizing codes C_(ch). The spread of the two channelbranches are summed and then complex-scrambled by a specific complexscrambling code C_(scramb). The complex-scrambled result is separatedinto real and imaginary and then transmitted, after being placed onrespective carriers. Noticeably, the same scrambling code is used forall physical channels in one cell, whereas different channelizing codesare used for different physical channels. Data and various controlinformation are transported to a receiver through the uplink anddownlink DPCHs subjected to the above-mentioned spreading andscrambling.

The TS S1.11 v1.1.0 specification also specified a primary commoncontrol physical channel (PCCPCH), which is a fixed rate downlinkphysical channel used to carry the broadcast channel (BCH), and asecondary common control physical channel (SCCPCH) used to carry theforward access channel (FACH) and the paging channel (PCH) at a constantrate. FIGS. 11A and 11B illustrate the frame structure of PCCPCH andSCCPCH, each having a pilot field. The TS S1.11 v1.1.0 specificationrecommended the pilot patterns for the PCCPCH and SCCPCH. Further, theTS S1.11 v1.1.0 specification recommended the pilot pattern of the DPCHchannel for the diversity antenna using open loop antenna diversitybased on space time block coding based transmit diversity (STTD) anddiversity antenna pilot patterns for PCCPCH and SCCPCH. Those patternscan be found in the TS S1.11 v1.1.0 specification, and detaileddescription is being omitted.

For frame synchronization, an autocorrelation function must be performedon the basis of the pilot pattern sequence. In the pilot sequencedesign, finding an autocorrelation of a sequence with the lowestout-of-phase coefficient is important to decrease the probability offalse alarm regarding the synchronization. A false alarm is determinedwhen a peak is detected when there should not be a peak detection.

Optimally, the result of the autocorrelation for a frame with a sequenceat a prescribed pilot bit should have same maximum values at zero andmiddle time shifts of one correlation period, which are different inpolarity, and the remaining sidelobes at time shifts other than zero andmiddle should have a value of zero. However, the various pilot patternsrecommended in the TS S1.11 v1.1.0 do not meet this requirement, both inthe uplink and downlink.

In an article entitled “Synchronization Sequence Design with DoubleThresholds for Digital Cellular Telephone” by Young Joon Song et al.(Aug. 18-20, 1998), the present inventor being a co-author, the articledescribes a correlator circuit for GSM codes where the out-of-phasecoefficients are all zero except one exception at zero and middle shifthaving a first peak and a second peak, where the first and second peaksare opposite in polarity, but the peaks are not equal to one another.Further, the article describes lowest out-of-phase coefficients of +4and −4. However, the article does not provide how such sequences andautocorrelation can be used to achieve the above described optimalresults, and the article does not provide sufficient disclosure that thesequences achieve or can achieve the lowest autocorrelation sidelobes.

As described above, the pilot patterns used as frame synchronizationwords or sequences do not achieve the optimal results. Further, thebackground pilot patterns do not rapidly and accurately perform theframe synchronization. Moreover, the above pilot patterns and framesynchronization sequences do not provide optimal cross-correlation andautocorrelation. Additionally, neither the TS specification nor thearticle provides a solution of the use of the pilot patterns forslot-by-slot double check frame synchronization scheme, and neitherdiscloses the use of the frame synchronization sequence for channelestimation.

SUMMARY OF THE INVENTION

An object of the present invention is to obviate at least the problemsand disadvantages of the related art.

An object of the present invention is to provide frame synchronizationwords resulting in optimal autocorrelation results.

A further object of the present invention is to eliminate or preventsidelobes.

A further object of the present invention is to provide maximum valuesat zero and middle time shifts.

Another object of the present invention is to provide a synchronizationword for at least one of rapid and accurate frame synchronization.

Another object of the present invention is to provide a slot-by-slotdouble check frame synchronization scheme.

Still another object of the present invention is to provide a framesynchronization word which can be used for channel estimation.

Still another object of the present invention is to provide goodcross-correlation and autocorrelation simultaneously.

The present invention can be achieved in a whole or in parts by a methodfor synchronizing a frame using an optimal pilot symbol, comprising thesteps of: (1) receiving a pilot symbol of each slot in the frame throughrespective physical channels on a communication link; (2) correlating areceived position of each of the pilot symbols to a corresponding pilotsequence; (3) combining and summing more than one results of thecorrelations, and deriving a final result from the correlations in whichsidelobes from the results of the correlations are offset; and (4)synchronizing the frame using the final result.

The pilot symbols are combined into each of the pilot sequences suchthat the final result of the correlations shows sidelobes with 0″ valuesexcluding particular positions of correlation periods. The particularpositions are starting points (x=0) of the correlation periods (x) andpoints of x/an integer. The pilot symbol is a combination of pilotsymbols in a form of (a,/a). The pilot sequence provides leastcorrelation resultants at positions excluding the starting points andhalf of the starting points in the correlation periods. The pilotsymbols excluding the pilot symbols used in the correlation is used in achannel estimation for detecting coherent. The pilot symbol of each slotin the frame is transmitted, with the pilot symbol contained in a pilotfield of an exclusive physical control channel among respectiveexclusive channels on the communication link. The pilot sequencesdifferent from each other on an up communication link are used in thecorrelation according to values of bits included in a pilot field of anexclusive physical control channel. The pilot sequences different fromeach other on a down communication link are used in the correlationaccording to a symbol rate of an exclusive physical control channel.

The present invention can be also achieved in a whole or in parts by amethod for synchronizing a frame using an optimal pilot symbol,comprising the steps of: (1) receiving a pilot symbol of each slot inthe frame through respective physical channels on a communication link;(2) correlating a received position of each of the pilot symbols to acorresponding pilot sequence; (3) combining and summing more than oneresults of the correlations, and deriving a final result from thecorrelations in which sidelobes from the results of the correlationshave minimum values and the results of the correlations at startingpoints and middle points of correlation periods have maximum values withdifferent polarity; and (4) synchronizing the frame using the finalresult.

The present invention can be achieved in a whole or in parts by a methodof eliminating sidelobes in a communication channel between a basestation and a mobile station, comprising the steps of: generatingcontrol signals and data signals within the communication channel, thecontrol signals having a first sequence of L-bits and a second sequenceof L-bits; generating a first set of prescribed values based on thefirst sequence, which has a first prescribed relationship with the firstset of prescribed values; generating a second set of prescribed valuesbased on the second sequence, which has a second prescribed relationshipwith the second set of prescribed values; and combining the first andsecond sets of prescribed values.

The present invention can be achieved in a whole or in parts by a methodof establishing a communication channel, the method comprising the stepsof: generating a plurality of frames; generating a L-number of slots foreach frame, each slot having a pilot signal of N-bits and acorresponding bit in each slot forming a word of L-sequence of pilotbits such that there is N number of words, wherein the number of bitvalues of two pilot bits which are the same between two adjacent wordsfrom 1 to L slots minus the number of bit values of two pilot bits whichare different between the two adjacent words from 1 to L is zero or aprescribed number close to zero.

The present invention can be achieved in a whole or in parts by a methodof establishing a communication channel having at least one of framesynchronization and channel estimation, the method comprising the stepsof: generating a plurality of frames; generating a L-number of slots foreach frame, each slot having a pilot signal of N-bits and acorresponding bit in each slot forming a word of L-sequence of pilotbits such that there is N number of words, wherein the words have atleast one of the following characteristics: cross-correlation betweentwo adjacent sequences used for frame synchronization is zero at zerotime shift, or cross-correlation between a word used for framesynchronization and a word used for channel estimation is zero at alltime shifts.

The present invention can be achieved in a whole or in parts by a methodof reducing sidelobes for frame synchronization, comprising the stepsof: generating a plurality of frame synchronization words, each framesynchronization word having a plurality of bits; performingautocorrelation functions on a pair of frame synchronization words togenerate a pair of prescribed value sets; and combining the pair ofprescribed value sets such that two peak values equal in magnitude andopposite in polarity are achieved at zero and middle time shifts.

The present invention can be achieved in a whole or in parts by a methodof generating pilot signals of a prescribed pattern within a framehaving L-number of slots, comprising the steps of: generating N-numberof pilot bits for each slot; and forming N-number of words of L-bitbased on above step, wherein a prescribed number of words is used forframe synchronization words and each frame synchronization word has afirst prescribed number b₀ of bit values of “0” and a second prescribednumber b₁ of bit values of “1”, such that b₁−b₀ is equal to zero or anumber close to zero.

The present invention can be achieved in a whole or in parts by acommunication link between a user equipment and a base stationcomprising a plurality of layers, wherein one of the layers is aphysical layer for establishing communication between the user equipmentand the base station and the physical layer has at least one of data andcontrol information, one of the control information being a pilot fieldof N-bits transmitted for L-number of slots such that N-number of wordsof L-bit are formed, wherein cross-correlation between two adjacentwords used for frame synchronization is zero at zero time shift orcross-correlation between a word used for frame synchronization and aword used for channel estimation is zero at all time shifts.

The present invention can be achieved in a whole or in parts by acorrelator circuit for at least one of a user equipment and a basestation, comprising: a plurality of latch circuits, each latch circuitlatching a word formed by a pilot bit from a plurality of slots; aplurality of correlators, each correlator coupled to a correspondinglatch circuit and correlating the word to a set of prescribed values;and a combiner that combines the set from each correlator such thatmaximum peak values of equal in magnitude and opposite in polarity areformed at zero and middle time shifts.

The present invention can be achieved in a whole or in parts by acommunication device comprising: means for transmitting at least one ofdata and control information; means for receiving at least one of dataand control information, wherein the receiving means includes: aplurality of latch circuits, each latch circuit latching a word formedby a pilot bit from a plurality of slots; a plurality of correlators,each correlator coupled to a corresponding latch circuit and correlatingthe word to a set of prescribed values; a plurality of buffers, eachbuffer coupled to a corresponding correlator to store the set ofprescribed values; and a combiner that combines the set from each buffersuch that maximum peaks of equal in magnitude and opposite in polarityare formed at zero and middle time shifts.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 generally illustrates a system, which uses CDMA modulationtechniques in communication between user and base stations;

FIG. 2 illustrates these three different propagation phenomena;

FIG. 3 depicts a block diagram of a transmitter and a receiver for timemultiplexed pilot symbols;

FIG. 4 illustrates a frame structure of an uplink DPCH based on the 3GPPRAN standard;

FIG. 5 is a table showing various information of the uplink DPCCH;

FIG. 6 is a table illustrating pilot bit patterns of the uplink DPCCH;

FIG. 7 shows a spreading/scrambling arrangement for the uplink DPCHbased on the 3GPP RAN standard;

FIG. 8 illustrates a frame structure of a downlink DPCH based on the3GPP RAN standard;

FIG. 9 is a table illustrating pilot symbol patterns contained in thedownlink DPCCH;

FIG. 10 illustrates a spreading/scrambling arrangement for the downlinkDPCH based on the 3GPP RAN standard;

FIGS. 11A and 11B illustrate the frame structure of PCCPCH and SCCPCH,respectively;

FIG. 12A is a table illustrating the frame synchronization words C₁ toC_(i-th) in accordance with a preferred embodiment of the presentinvention;

FIG. 12B is a table illustrating the autocorrelation function of thesequences of pilot bits;

FIG. 13A illustrates addition of two autocorrelation functions;

FIG. 13B illustrates addition of the four autocorrelation functions;

FIGS. 14A and 14B are tables illustrating the pilot patterns inaccordance with a preferred embodiment of the present invention foruplink DPCCH;

FIG. 14C is a table illustrating the mapping relationship between the 8synchronization words C₁-C₈ of FIG. 12A and shaded pilot bit patterns ofFIGS. 14A and 14B;

FIG. 14D illustrates a correlation circuit for frame synchronizationbased on pilot bits of the uplink DPCCH in accordance with a preferredembodiment of the present invention;

FIG. 14E is a table illustrating the correlation results at pointsA₁-A₄, and the summing of the correlation results at point B of FIG.14D.

FIG. 14F is a table illustrating various results of the addition ofcorrelation results based on the uplink pilot patterns of the framesynchronization words in accordance with the preferred embodiment of thepresent invention;

FIG. 14G illustrates a correlator circuit for frame synchronizationbased on pilot bit sequences of an uplink DPCCH in accordance with analternative embodiment;

FIG. 14H illustrates the receiver circuit of a base station or a userequipment to recover the received spread signal including the framesynchronization words in the pilot field;

FIG. 14I illustrates results of correlation circuit using the pilotpattern of the technical specification;

FIG. 14J illustrates a time shift graph of the summation of results ofFIG. 14I;

FIG. 15A illustrates the pilot symbol patterns for downlink DPCH;

FIG. 15B illustrates the mapping relationship between the 8 framesynchronization words of FIG. 12A, and shaded pilot symbol pattern ofFIG. 15A;

FIG. 15C illustrates a correlation circuit for frame synchronization fordownlink DPCCH in accordance with the preferred embodiment;

FIG. 16A illustrates pilot symbol pattern of PCCPCH;

FIG. 16B illustrates the mapping relationship between thesynchronization words C₁-C₈ of FIG. 12A, and the shaded pilot symbolpatterns of FIG. 16A;

FIG. 16C illustrates pilot symbol pattern of SCCHPCH;

FIG. 16D illustrates the mapping relationship between thesynchronization words C₁-C₈ of FIG. 12A, and the shaded pilot symbolpatterns of FIG. 16C;

FIGS. 17A-17C illustrate addition of autocorrelation functions of framesynchronization word of the preferred embodiment and current pilotpatterns (described in TS S1.11 v1.1.0 specification) for DPCHs andPCCPCH;

FIG. 18A illustrates the parameters used for obtaining P_(D), P_(FA),and P_(S) on uplink DPCCH and downlink DPCH over additive white Gaussiannoise (AWGN);

FIG. 18B illustrates the probability of detection P_(D) on downlinkDPCCH over AWGN channel;

FIG. 18C illustrates the probability of false alarm P_(FA) on downlinkDPCCH over AWGN channel;

FIG. 18D illustrates the probability of a frame synchronizationconfirmation success P_(S) on downlink DPCCH over AWGN channel;

FIG. 19A illustrates pilot symbol patterns of downlink DPCH for thediversity antenna using a space time block coding based transmitdiversity (STTD);

FIG. 19B illustrates the mapping relationship between the 8 words C₁-C₈of FIG. 12A and shaded pilot symbol patterns of FIG. 19A;

FIG. 19C illustrates the diversity antenna pilot symbol pattern forPCCPCH;

FIG. 19D illustrates the mapping relationship between the words C₁-C₈ ofFIG. 12A and shadowed pilot symbol patterns of FIG. 19C;

FIG. 19E illustrates the pilot symbol pattern for the diversity antennawhen STTD encoding is used on the SCCPCH;

FIG. 19F illustrates the mapping relationship between the words C₁-C₈ ofFIG. 12A and shaded pilot symbol patterns of FIG. 19E;

FIG. 20A is a table illustrating frame synchronization words C₁-C₁₆(i=16) and autocorrelated function in accordance with another preferredembodiment of the present invention;

FIG. 20B is a table illustrating the autocorrelation function of thepilot bits of each frame synchronization word classified in the PCSP;

FIG. 20C illustrates the pilot bit pattern of uplink DPCCH;

FIG. 20D illustrates a mapping relationship between the alternativeframe synchronization words C₁-C₁₆ of FIG. 20A and the shaded framesynchronization words of FIG. 20C;

FIGS. 20E and 20F illustrate the pilot symbol pattern of downlink DPCH;

FIG. 20G illustrates a mapping relationship between the alternativeframe synchronization words C₁-C₁₆ of FIG. 20A and the shaded framesynchronization words of FIGS. 20E and 20F;

FIG. 20H illustrates the pilot symbol pattern of downlink PCCPCH;

FIG. 20I illustrates a mapping relationship between the alternativeframe synchronization words C₁-C₁₆ of FIG. 20A and the shaded framesynchronization words of FIG. 20H.

FIG. 21 illustrates a preferred embodiment for the new framesynchronization words C₁-C_(i-th);

FIG. 22A illustrates the addition of two auto-correlation functions;

FIG. 22B illustrates the addition of two cross-correlation functionsbetween the two frame synchronization words within the same class;

FIG. 22C illustrates the addition of four auto-correlation functions;

FIG. 22D illustrates the addition of four cross-correlation functionsbetween the four frame synchronization words of two classes;

FIG. 23A illustrates the pilot bit patterns on uplink DPCCH withN_(pilot)=2, 3, and 4;

FIG. 23C illustrates the pilot bit patterns on uplink DPCCH withN_(pilot)=2,3, and 4 in accordance with an alternative embodimentcompared to FIG. 23A;

FIGS. 23E and 23F illustrate the pilot bit patterns on uplink DPCCH withN_(pilot)=5, 6, 7, and 8;

FIGS. 23B and 23D illustrate the mapping relationship between the framesynchronization words of FIG. 21, and shaded frame synchronization wordsof FIGS. 23A and 23D, respectively;

FIG. 23G illustrates the snapping relationship between the framesynchronization words of FIG. 21, and the shaded frame synchronizationwords of FIGS. 23E and 23F;

FIG. 23H illustrates the structure of random access channel;

FIG. 23I illustrates the random access message control fields;

FIG. 23J illustrates the pilot bit pattern of the RACH;

FIG. 24A illustrates the pilot symbol patterns on downlink DPCH whenN_(pilot)=2, 4, 8, and 16;

FIG. 24B illustrates the mapping relationship between the framesynchronization words C₁-C₈ of FIG. 21 and shaded pilot symbol patternsof FIG. 24A;

FIG. 24C illustrates the pilot symbol patterns of downlink DPCH for thediversity antenna using STTD;

FIG. 24D illustrates the mapping relationship between the framesynchronization words C₁-C₈ of FIG. 21 and shaded pilot symbol patternsof FIG. 24C;

FIG. 25A illustrates the pilot symbol patterns for downlink SCCPCH forN_(pilot)=8 and 16;

FIG. 25B illustrates the mapping relationship of the framesynchronization words C₁-C₈ of FIG. 21 and shaded pilot symbol patternsof FIG. 25A;

FIG. 25C illustrates the pilot symbol patterns of downlink SCCPCH forNpilot=8 and 16 for the diversity antenna using STTD;

FIG. 25D illustrates the mapping relationship between the framesynchronization words C₁-C₈ of FIG. 21 and shaded pilot symbol patternsof FIG. 25C;

FIG. 26A illustrates the parameters used to evaluate the performance ofthe pilot bit pattern on uplink DPCCH over AWGN;

FIG. 26B illustrates the probability of frame synchronizationconfirmation success P_(S) on uplink DPCCH with N_(pilot)=6 over AWGNchannel;

FIG. 26C illustrates the probability of a false alarm P_(FA) on uplinkDPCCH with N_(pilot)=6 over AWGN channel; and

FIG. 27 is a comparision chart between the embodiments for 15 timeslotsand 16 slots.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The new frame synchronization words in accordance with the preferredembodiment have the lowest out-of-phase values of autocorrelationfunction with two peak values equal in magnitude and opposite inpolarity at zero and middle shifts. The frame synchronization words aresuitable for frame synchronization confirmation since by simply addingautocorrelation functions of such words, double maximum correlationvalues equal in magnitude and opposite polarity at zero and middleshifts can be achieved. This property can be used to double-check framesynchronization timing and reduce the synchronization search time.

The UE establishes downlink chip synchronization and framesynchronization based on the Primary CCPCH synchronization timing andthe frame offset group, slot offset group notified from the network. Theframe synchronization can be confirmed using the frame synchronizationword. The network establishes uplink channel chip synchronization andframe synchronization based on the frame offset group and slot offsetgroup. The frame synchronization can also be confirmed using the framesynchronization word.

When long scrambling code is used on uplink channels or downlinkchannels, failure in frame synchronization confirmation using framesynchronization words always means losing frame and chipsynchronizations since the phase of long scrambling code repeats everyframe. Whereas in the case of short scrambling code on uplink DPCCH,failure in frame synchronization confirmation does not always implieslosing chip synchronization since the length of short scrambling code is256 and it corresponds to one symbol period of uplink DPCCH with SF=256.Thus, the frame synchronization word of pilot pattern can detectsynchronization status and this information can be used in RRCConnection Establishment and Release Procedures of Layer 2.

FIG. 12A is a table illustrating the frame synchronization words C₁ toC_(i-th) in accordance with a preferred embodiment of the presentinvention, where each word comprises L number (L>1) of sequence of pilotbits from a prescribed bit position of the N_(pilot) bits (N_(pilot)>0)from each slot of L number of slots. In the preferred first embodimentdescribed hereinafter, the number of synchronization words i equals 8,the number of slots L=16 and the number of pilot bits N_(pilot) in eachslot is between 4 and 16, but the present invention is applicable todifferent variations of i, L, and N_(pilot).

The synchronization words C₁-C₈ of the preferred embodiment can bedivided into 4 classes (E-H, referred to as Preferred CorrelationSequence Pair (PCSP)) according to the autocorrelation function of thesynchronization words, as follows:E={C₁, C₅}F={C₂, C₆}G={C₃, C₇}H={C₄, C₈}

FIG. 12B is a table illustrating the autocorrelation function of 1 to 16sequences of pilot bits of each frame synchronization word classified inclasses E, F, G and H within one correlation period from a time shift of0 to 15. As shown in FIGS. 12A and 12B, each class contains 2 sequences,and sequences of the same class have the same autocorrelation function.From FIG. 12B, the synchronization words have the lowest out-of-phasevalues of autocorrelation function with two peak values equal inmagnitude and opposite in polarity at zero and middle shifts. Moreover,the results R₁ and R₂ of the autocorrelation function are complements ofeach other. The following relationships between the autocorrelationfunctions are expressed in equations (1)-(4):R _(E)(τ)=R _(F)(τ)=R _(G)(τ)=R _(H)(τ), τis even  (1)R _(E)(τ)=−R _(F)(τ), τis odd  (2)R _(G)(τ)=−R _(H)(τ), τis odd  (3)R _(i)(τ)+R _(i)(τ+8)=0i∈{E,F,G,H}, for all τ  (4)From equations (1), (2), and (3), the following equation is obtained.R _(E)(τ)+R _(F)(τ)=R _(G)(τ)+R _(H)(τ), for all τ  (5)

The addition of two autocorrelation functions R_(E)(τ) and R_(F)(τ), orR_(G)(τ) and R_(H)(τ) becomes the function with two peak values equal inmagnitude and opposite in polarity at zero and middle shifts, and allzero values except the zero and middle shifts, which is depicted in FIG.13A, where the peak values equal 2*L or −2*L. In the preferredembodiment, the peak values of FIG. 13A are 32 and −32, since L=16. Theother combinations such as (R_(E)(τ)+R_(G)(τ)), (R_(E)(τ)+R_(H)(τ)),(R_(F)(τ)+R_(G)(τ)), and (R_(F)(τ)+R_(H)(τ)) do not have the same valueas in FIG. 13A. By using the derived properties of the framesynchronization words, the following property is achieved.

$\begin{matrix}{{{\sum\limits_{i = 1}^{2a}{R_{i}(\tau)}} = {\alpha \cdot \left( {{R_{E}(\tau)} + {R_{F}(\tau)}} \right)}},{1 \leq \alpha \leq 4}} & (6)\end{matrix}$where R_(i)(τ) is the autocorrelation function of sequence C_(i), 1≦i≦8.

The addition of the four autocorrelation functions is illustrated inFIG. 13B, which is the same as FIG. 13B except that the maximum value isdoubled to 4*L or −4*L (the maximum values being 64 and −64 for thepreferred embodiment) since (R_(E)(τ)+R_(F)(τ)+R_(G)(τ)+R_(H)(τ))=2(R_(E)(τ)+R_(F)(τ)) by equations (5) and (6). This property allows thedouble-checking of the frame synchronization timing and the reduction ofthe synchronization search time.

First Embodiment for Uplink DPCCH

FIGS. 14A and 14B are tables illustrating the pilot patterns inaccordance with a preferred embodiment of the present invention foruplink DPCCH with N_(pilot)=5, 6, 7, and 8. The shaded pattern of FIGS.14A and 14B are used for frame synchronization (which can also be usedfor channel estimation), and the pilot bit other than the framesynchronization words (e.g., channel estimation) has a value of 1. FIG.14C is a table illustrating the mapping relationship between the 8synchronization words C₁-C₈ of FIG. 12A and shaded pilot bit patterns ofFIGS. 14A and 14B, where frame synchronization words C₁, C₂, C₃, and C₄are the elements of the set {E, F, G, and H}, respectively. The resultsof FIGS. 13A and 13B are obtained by α=1 and 2 in equation (6),respectively, which allows a double-check of the frame synchronizationtiming and a reduction of the synchronization time on uplink DPCCH withN_(pilot)=5, 6, 7, and 8.

For example, the frame synchronization words at bit #1 (C₁), at bit #2(C₂), at bit #4 (C₃) and at bit #5 (C₄) are used in the autocorrelationprocess for the frame synchronization when N_(pilot)=6. For N_(pilot)=8,the frame synchronization words at bit #1 (C₁), at bit #3 (C₂), at bit#5 (C₃) and at bit #7 (C₄) are used in the autocorrelation process forthe frame synchronization. For N_(pilot)=5, 6, 7, and 8 in each slot, atotal of four frame synchronization words are used. As a result, sinceone radio frame has sixteen timeslots, the number of pilot bits used forthe frame synchronization is only 64 per frame in the preferredembodiment. As can be appreciated, the number of words used for framesynchronization can vary depending on variations of N_(pilot). Forexample, when N_(pilot)=1, one of the frame synchronization words C₁-C₈can be used for both frame synchronization and channel estimation due tothe novel feature of the preferred embodiment.

FIG. 14D illustrates a correlation circuit for frame synchronizationbased on pilot bits of the uplink DPCCH in accordance with a preferredembodiment of the present invention when frame synchronization wordsC₁-C₄ are used. The frame synchronization words C₁-C₄ are latched inlatch circuits 31-34, respectively. The correlators 41-44 performcorrelation function R(x), where x=0 to L−1, of the framesynchronization words C₁-C₄, respectively, to generate the correlationresults A₁-A₄, which are stored in buffers 51-53.

FIG. 14E is a table illustrating the correlation results at pointsA₁-A₄, and the summing of the correlation results at point B. As shown,the result has maximum values of opposite polarity at zero and middletime shifts R(0) and R(8). Further, the remaining sidelobes at timeshifts other than zero and middle have values of zero after the additionat point B. The sidelobes are eliminated or minimized, and the resultsat point B correspond to the optimal results of FIG. 13B.

FIG. 14F is a table illustrating various results of the addition ofcorrelation results of points A₁-A₄ based on the uplink pilot patternsof the frame synchronization words C₁-C₄ in accordance with thepreferred embodiment of the present invention. The respective additionof the autocorrelation results of points (A₁+A₂), (A₃+A₄), (A₁+A₄) and(A₂+A₃) exhibit the same characteristics of the optimal resultsillustrated in FIG. 13A.

FIG. 14G illustrates a correlator circuit for frame synchronizationbased on pilot bit sequences of an uplink DPCCH in accordance with analternative embodiment. The elements are the same as the correlatorcircuit of FIG. 14D. The frame synchronization words of (C₁ and C₂), (C₂and C₃), (C₃ and C₄), or (C₄ and C₁) are correlated and summed toprovide the results at point D. The summation result at point D of FIG.14G is similar to the correlator circuit of FIG. 14D other than themaximum values of opposite polarity being 2*L (32) and −2*L (−32),rather than 4*L (64) and −4*L (−64), respectively, corresponding to theresults of FIG. 14F and optimal results of FIG. 13A.

FIG. 14H illustrates the receiver circuit 60 of a base station or a userequipment to recover the received spread signal including the framesynchronization words in the pilot field. After despreading the receivedspread signal by the despreading circuit 61, the channel estimator andframe synchronizer 62 performs the channel estimation and the framesynchronization based on the pilot field. The Rake combiner 63 uses theresults of the channel estimator and frame synchronizer, and after rakecombining, the data is deinterleaved by the deinterleaving circuit 64 inthe reverse order of the transmitter side. Thereafter, the data isrecovered after decoding by a decoder 65.

The advantages of the present invention can be readily discerned basedon comparison of the frame synchronization words previously recommendedin TS S1.11 v1.1.0 specification and the frame synchronization wordsfor, e.g., N_(pilot)=6. Applying the same principle of equations (1)-(6)and the correlator circuit of FIG. 14D, the results in FIG. 14I areobtained for the pilot pattern indicated in the technical specification.When the summation result at point B is mapped on a time shift graph,the problem of sidelobes is readily apparent, as shown in FIG. 14J. Inother words, there is no maximum peak values of opposite polarity atzero and middle time shifts, and sidelobes are present at time shiftsother than zero and middle.

As described in the background art, obtaining good cross-correlation andautocorrelation simultaneous is difficult to achieve, wherecross-correlation relates to different words at different time shiftsand autocorrelation relates to same sequences which are time shiftedversion. The good cross-correlation and autocorrelation of the presentinvention is based on unique properties of the frame synchronizationwords.

The unique characteristics of the frame synchronization words inaccordance with the preferred embodiment can be readily discerned inview of FIGS. 12, 14A and 14B. As shown in frame synchronization wordsC₁-C₈ of FIG. 12, each word has substantially the same number of 1 and0. In other words, the number (b₁) of pilot bits of a framesynchronization words having a value of 1 minus the number (b₀) of pilotbits of the frame synchronization having a value of 0 is equal to zeroor close to zero. In the preferred embodiment, when there are evennumber of slot numbers, there are the same number of pilot bits having avalue of 1 and 0 in a single frame synchronization word such that b₁−b₀is zero. As can be appreciated, when there are an odd number of pilotbits in a single frame synchronization word, the result of b₁−b₀ is plusor minus one, e.g., close to zero.

The second characteristic of the frame synchronization words can bediscerned by an examination between a pair of adjacent framesynchronization words (shaded patterns of FIGS. 14A and 14B forN_(pilot)=5, 6, and 7), or between a pair of adjacent framesynchronization word and channel estimation word (shaded and non-shadedpatterns of FIGS. 14A and 14B for N_(pilot)=5, 6, 7, and 8). Generally,the number (b₃) of bit values which are the same (0, 0 and 1,1) betweena pair of adjacent words (i.e., between two adjacent framesynchronization words, or between a frame synchronization word and achannel estimation word, which are adjacent) minus the number (b₄) ofbit values which are different (1,0 or 0,1) between adjacent words(i.e., between two adjacent frame synchronization words, or between aframe synchronization word and a channel estimation word, which areadjacent) equals zero or a prescribed number close to zero.

In the preferred embodiment, the number (b₃) of pilot bit values whichare the same between two adjacent words equals the number (b₄) of pilotbit value which are different between the two adjacent words, i.e.,b₃−b₄=0. In the preferred embodiment, when the N_(pilot)=5, between twosynchronization words of C₁ at bit #0 and C₂ at bit #1, there samenumber of pilot bit values which are the same (0,0 and 1,1) and pilotbit values which are different (1,0 and 0,1) from slot #1 to slot #16,as shown in FIG. 14A. Similarly, between a synchronization word C₂ atbit #1 and a channel estimation word at bit #2, there same number ofpilot bit values which are the same (0,0 and 1,1) and pilot bit valueswhich are different (1,0 and 0,1) from slot #1 to slot #16. The sameapplies between two adjacent words at bit #2 and bit #3, and between twoadjacent words at bit #3 and bit #4. The above also applies to adjacentwords of N_(pilot)=6, 7 and 8. As can be appreciated, when an odd numberof slots are used, the result of b₃−b₄ equals plus or minus one, e.g.,close to zero.

As a result of such a characteristic, cross-correlation between twoadjacent words used for frame synchronization is zero (orthogonal) atzero time shift. Further, the cross-correlation between a word used forframe synchronization and the sequence used for channel estimation iszero (orthogonal) at all time shifts. In other word, within N_(pilot)number of words of L-bits, there are an even number of words used forframe synchronization, but all words perform channel estimation, whereinbetween adjacent words used for frame synchronization, there issubstantially zero cross-correlation. Moreover, the words used for framesynchronization has substantially zero cross-correlation with words notused for frame synchronization, i.e., channel estimation, at any timeshifts.

Further, each N_(pilot) words corresponds to a prescribed number by anautocorrelation function such that when a pair from a set ofautocorrelated results corresponding to words used for framesynchronization is combined, two peak values equal in magnitude andopposite in polarity are achieved at zero and middle time shift whilesidelobes are substantially eliminated at time shifts other than zeroand middle. Autocorrelation in accordance with the present invention canbe generally defined as a correlation between a word and its timeshifted replica (including replica at zero time shift), wherecorrelation is the number of bit values which are the same between twowords minus the number of bit values which are different between thesame two words. Further, as shown in FIG. 12B, R₁ and R₂ are complementsof each other.

First Embodiment for Downlink DPCH

FIG. 15A illustrates the pilot symbol patterns for downlink DPCH forN_(pilot)=4, 8 and 16, where two pilot bits form a symbol since theright bit is used for the I channel branch and the left bit is used forthe Q channel branch. In the preferred embodiment, N_(pilot)=4 can beused for 8 ksps (kilo symbols per second); N_(pilot)=8 can be used for16, 32, 64, and 128 ksps; and N_(pilot)=16 can be used for 256, 512, and1024 ksps. The shaded symbols of FIG. 15A can be used for framesynchronization, and the value of pilot symbol other than for framesynchronization word, e.g., channel estimation (channel estimationword), is 11. The results of FIG. 15A is obtained by allowing α=1 forN_(pilot)=4, α=2 for N_(pilot)=8, and α=4 for N_(pilot)=16 in equation(6) for downlink DPCH.

FIG. 15B illustrates the mapping relationship between the 8 framesynchronization words of FIG. 12A, and shaded pilot symbol pattern ofFIG. 15A. For example, in the preferred embodiment of N_(pilot)=4, thesymbol #1 includes two frame synchronization words of C₁ (for the Ichannel branch I-CH, i.e., left sequence of bits from slot #1 to slot#16) and C₂ (for the Q channel branch Q-CH, i.e., right sequence of bitsfrom slot #1 to slot #16). For N_(pilot)=8 and N_(pilot)=16, thecorrespondence of words to channels for corresponding symbols isself-explanatory in FIG. 15B. Similar to the uplink DPCCH, slot-by-slotdouble-check of the frame synchronization timing and a reduction of theframe synchronization search time can be achieved by using theautocorrelation property of the pilot symbol pattern based on equation(6).

Because the frame synchronization words of the downlink DPCH is based onframe synchronization words of FIG. 12A, the characteristics describedfor uplink DPCCH is applicable to downlink DPCH. For example, the number(b₃) of bit values which are the same (0,0 and 1,1) between adjacentwords (i.e., between synchronization word of I channel branch andsynchronization word of Q channel branch of a frame synchronizationsymbol, or between a channel estimation word of the Q channel branch anda frame synchronization word of the I channel branch, which areadjacent, or between a frame synchronization word of the Q channelbranch and a channel estimation word of the I channel branch, which areadjacent) minus the number (b₄) of bit values which are different (1,0and 0,1) between adjacent words (i.e., between synchronization word of Ichannel branch and synchronization word of Q channel branch of a framesynchronization symbol, or between a channel estimation word of the Qchannel branch and a frame synchronization word of the I channel branch,which are adjacent, or between a frame synchronization word of the Qchannel branch and a channel estimation word of the I channel branch,which are adjacent) equals zero or a prescribed number close to zero.

For example, for N_(pilot)=8, between the symbols #0 and #1, the numberof a pair of adjacent bits, i.e., one bit from the Q channel branch ofthe symbol #0 and one bit from the I channel branch of the symbol #1,having bit values of 1,1 and 0,0 is the same as the number of adjacentbits having bit values of 1,0 and 0,1. In other words, b₃−b₄=0. As canbe appreciated, if the number of slots L is an odd number, the result ofb₃−b₄ is plus or minus one, e.g., a prescribed number close to zero.

FIG. 15C illustrates a correlation circuit for frame synchronization fordownlink DPCCH of N_(pilot)=8 in accordance with the preferredembodiment. The operation and components are the same as the correlationcircuit of FIG. 14D for uplink DPCCH, except for the reception of Ichannel branch and Q channel branch synchronization words. The resultsof points A₁-A₄ and point B is the same as FIG. 14E. Similarly, thesidelobes are eliminated or minimized, and the results correspond to theoptimal results of FIG. 13B. Because the number of pilot symbols (orpilot bits) used for the frame synchronization is 2-symbols per slot (or4 bit per slot), 32 pilot symbols (or 64 pilot bits) are used in eachradio frame for the frame synchronization.

For N_(pilot)=4 in the downlink DPCCH, the correlator circuit of FIG.14G can be used. In such a case, the I and Q channel framesynchronization words are inputted to the correlator circuit. Thesummation result would be the same as FIG. 14F, which corresponds to theoptimal results of FIG. 13A. In this case, the number of pilot symbols(or pilot bits) used for the frame synchronization is 1 symbol per slot(or 2 bits per slot), and 16 symbols (or 32 pilot bits) are used in eachradio frame for the frame synchronization.

As per N_(pilot)=16 in the downlink DPCCH, the correlation circuit ofFIG. 15C can be expanded to accommodate the additional framesynchronization words of the I and Q channel branches of pilot symbol #5and symbol #7. The summation result would be similar to the optimalresults of FIG. 13B, but the maximum peak values of opposite polaritywould be 128 (8*L) and −128 (−8*L). Further, the number of pilot symbols(or pilot bits) used for the frame synchronization is 4 symbols per slot(or 8 bits per slot), and 64 pilot symbols (or 128 pilot bits) are usedin each radio frame for the frame synchronization.

First Embodiment of Downlink PCCPCH and SCCPCH

FIG. 16A illustrates pilot symbol pattern of PCCPCH. The shaded symbolscan be used for frame synchronization, and the value of pilot symbolother than for frame synchronization is 11. FIG. 16B illustrates themapping relationship between the synchronization words C₁-C₈ of FIG.12A, and the shaded pilot symbol patterns of FIG. 16A. A double-checkframe of the synchronization timing and the reduction of thesynchronization search time can be achieved with α=1 or 2 in equation(6).

FIG. 16C illustrates pilot symbol pattern of SCCPCH. The shaded symbolscan be used for frame synchronization, and the value of pilot symbolother than for frame synchronization is 11. FIG. 16D illustrates themapping relationship between the synchronization words C₁-C₈ of FIG.12A, and the shaded pilot symbol patterns of FIG. 16C.

As shown above, the frame synchronization words of PCCPCH and SCCPCH isbased on the frame synchronization words C₁-C₈, and the disclosure forthe uplink DPCCH and the downlink DPCH is applicable. Hence, a detaileddescription regarding the various characteristics includingcross-correlation and autocorrelation, operations and implements areomitted since one of ordinary skill in the art can readily appreciatethe present invention based on the uplink DPCCH and downlink DPCH.

As described above, the non-shaded symbols are the pilot symbols notused for frame synchronization comprises symbols of 11, and the shadedsymbols are used for frame synchronization. The frame synchronizationwords of the pilot pattern are used for frame synchronizationconfirmation, and the summation of autocorrelated values for each framesynchronization words is required. The property of summation ofautocorrelated values of frame synchronization words is very important.

The addition of autocorrelation functions of frame synchronization wordof the preferred embodiment and current pilot patterns (described in TSS1.11 v1.1.0 specification) for DPCHs and PCCPCH are depicted in FIG.17A (N_(pilot)=4), FIG. 17B (N_(pilot)=8) and FIG. 17C (N_(pilot)=16).As shown, the current pilot patterns have non-zero out-of-phaseautocorrelation function with peak value at zero shift, whereas theframe synchronization words of the preferred embodiment have zeroout-of-phase autocorrelation function with two peak values equal inmagnitude and opposite in polarity at zero and middle time shifts(delays).

Correlation to a prescribed frame synchronization word is optimum methodfor frame synchronization. Since the frame synchronization word of pilotpattern is used for frame synchronization confirmation, the followingevents and parameters are used to evaluate the performance of framesynchronization confirmation using the frame synchronization words ofthe preferred embodiment and the current pilot patterns:

-   H₁: The event that the correlator output exceeds the predetermined    threshold when the code phase offset between the received shadowed    column frame synchronization word and its corresponding receiver    stored frame synchronization word is zero.-   H₂: The event that the correlator output exceeds the predetermined    threshold when the code phase offset between the received shadowed    column frame synchronization word and its corresponding receiver    stored frame synchronization word is not zero.-   H₃: One event of H₁ and no event of H₂ for one frame.-   H₄: The event that the correlator output exceeds the predetermined    threshold or is smaller than −1×(predetermined threshold) when the    code phase offset between the received shadowed column frame    synchronization word and its corresponding receiver stored frame    synchronization word is 0 or 8, respectively.-   H₅: The event that the correlator output exceeds the predetermined    threshold or is smaller than −1×(predetermined threshold) when the    code phase offset between the received shadowed column frame    synchronization word and its corresponding receiver stored frame    synchronization word is not 0 and 8.-   H₆: One event of H₄ and no event of H₅ for one frame.-   P_(D): Probability of a detection.-   P_(FA): Probability of a false alarm.-   P_(S): Probability of a frame synchronization confirmation success    for one frame.

From the above definitions, when the current pilot pattern is used forframe synchronization confirmation, the probability of a detection and afalse alarm can be expressed as:P _(D) =Prob(H ₁)  (7)P _(FA) =Prob(H ₂)  (8)

The probability of a frame synchronization confirmation success for oneframe becomes P_(S)=Prob(H₃) and it can be expressed asP _(S) =P _(D)(1−P _(FA))¹⁵  (9)

Whereas in the case of the frame synchronization words of the preferredembodiment, as has been stated, double thresholds are needed fordouble-check frame synchronization, and the probability of a detectionand a false alarm can be expressed as:P _(D) =Prob(H ₄)  (10)P _(FA) =Prob(H ₅)  (11)

Similarly, in the case of frame synchronization words of the preferredembodiment, the probability of a frame confirmation success for oneframe becomes P_(S)=Prob(H₆) and it is given byP _(S) =P _(D)(1−P _(FA))¹⁴  (12)

From equations (9) and (12), the probability of a frame synchronizationconfirmation is greatly affected by the probability of a false alarmsince P_(S) is proportional to P_(D) and (1−P_(FA))¹⁴ or (1−P_(FA))¹⁵.For example, assume that P_(FA)=10⁻¹, then (1−P_(FA))¹⁴=0.2288 and(1−P_(FA))¹⁵=0.2059. Now let P_(FA)=10⁻³, then (1−P_(FA))¹⁴=0.9861 and(1−P_(FA))¹⁵=0.9851. The performance of frame synchronization can besufficiently evaluated by selecting the threshold so that the P_(FA) ismuch smaller than (1−P_(D)).

The parameters of FIG. 18A are used for obtaining P_(D), P_(FA), andP_(S) on uplink DPCCH and downlink DPCH over additive white Gaussiannoise (AWGN). FIG. 18B illustrates the probability of detection P_(D) ondownlink DPCCH with N_(pilot)=4 over AWGN channel, FIG. 18C illustratesthe probability of false alarm P_(FA) on downlink DPCCH with N_(pilot)=4over AWGN channel, and FIG. 18D illustrates the probability of a framesynchronization confirmation success P_(S) on downlink DPCCH withN_(pilot)=4 over AWGN between the pilot pattern of the preferredembodiment and the current pilot pattern, where P_(D), P_(FA), and P_(S)are given as a function of E_(b)/N₀ ratio (E_(b)=energy per bit,N₀=noise power spectral density).

The P_(D) and P_(S) of the pilot patterns of the preferred embodimentare greater than that of current pilot pattern. Furthermore, the P_(FA)of the pilot patterns in accordance with the preferred embodiment arealso smaller than that of the current pilot patterns. The theoreticalequations (9) and (12) are identical to simulation results of FIG. 18D.Therefore, there is significant difference between the framesynchronization performance of pilot patterns of the preferredembodiment and that of current pilot pattern. For example, from FIG.18D, there is 3 dB gain at P_(S)=0.93 by employing the pilot patterns ofthe preferred embodiment.

The frame synchronization words of the preferred embodiment areespecially suitable for frame synchronization confirmation. By addingthe autocorrelation functions of shaded frame synchronization words,double maximum values equal in magnitude and opposite polarity at zeroand middle shifts are obtained. This property can be used toslot-by-slot and double-check frame synchronization timing and reducethe synchronization search time. The performance of framesynchronization confirmation over AWGN using pilot pattern illustratethe significant differences between the frame synchronizationperformance of the pilot pattern of the preferred embodiment and thecurrent pilot pattern.

First Embodiment of Downlink DPCH, PCCPCH and SCCPH for STTD Diversity

FIG. 19A illustrates new pilot symbol patterns of Downlink DPCH for thediversity antenna using a space time block coding based transmitdiversity (STTD). For the diversity pilot symbol pattern on downlinkDPCH, STTD is applied to the shaded pilot symbols #1 and #3 forN_(pilot)=8, and the shaded pilot symbols #1, #3, #5, and #7 forN_(pilot)=16. The non-shaded pilot symbols #0 and #2 for N_(pilot)=8,and non-shaded pilot symbols #0, #2, #4, and #6 for N_(pilot)=16 areencoded to be orthogonal to the pilot symbol of FIG. 15A. However, thediversity pilot pattern for downlink DPCH with N_(pilot)=4 are STTDencoded since STTD encoding requires two symbols. FIG. 19B illustratesthe mapping relationship between the 8 words C₁-C₈ of FIG. 12A andshaded pilot symbol patterns of FIG. 19A.

FIG. 19C illustrates the new diversity antenna pilot symbol pattern forPCCPCH. The pilot symbols of FIG. 19C are encoded to be orthogonal tothe pilot symbols of FIG. 16A. FIG. 19D illustrates the mappingrelationship between the words C₁-C₈ of FIG. 12A and shadowed pilotsymbol patterns of FIG. 19C.

FIG. 19E illustrates the new pilot symbol pattern for the diversityantenna when STTD encoding is used on the SCCPCH. For the diversitypilot symbol pattern on SCCPCH, STTD is applied to the shaded pilotsymbols #1, and #3 of N_(pilot)=8, and shaded pilot symbols #1, #3, #5and #7 of N_(pilot)=16 in FIG. 19E, whereas the non-shaded pilot symbols#0 and #2 of N_(pilot)=8, and non-shaded #0, #2, #4, #6 of N_(pilot)=16are encoded to be orthogonal to those of FIG. 16C. FIG. 19F illustratesthe mapping relationship between the words C₁-C₈ of FIG. 12A and shadedpilot symbol patterns of FIG. 19E.

Since the above is based on words C₁-C₈, the previous discussionregarding the uplink DPCCH and downlink DPCH, PCCPCH and SCCPH isreadily applicable. One of ordinary skill in the art can readilyappreciate the features for downlink using diversity antenna based onprevious disclosure, and a detailed disclosure is omitted.

Alternative Embodiments for Uplink DPCCH and Downlink DPCH and PCCPCH

FIG. 20A is a table illustrating frame synchronization words C₁-C₁₆(i=16) and autocorrelated function in accordance with another preferredembodiment of the present invention. The frame synchronization wordsC₁-C₁₆ can be classified into the PCSP of the first embodiment, asfollows:E={C₁, C₃, C₉, C₁₁}F={C₂, C₄, C₁₀, C₁₂}G={C₅, C₇, C₁₃, C₁₅}H={C₆, C₈, C₁₄, C₁₆}

The classification of the alternative frame synchronization words C₁-C₁₆are also applicable to equations (1)-(6), and have the same propertiesand characteristics of the first embodiment. FIG. 20B is a tableillustrating the autocorrelation function of the pilot bits of eachframe synchronization word classified in the PCSP. In this particularcase, each class contains four sequences and the sequences of the sameclass have the same autocorrelation function.

FIG. 20C illustrates the pilot bit pattern of uplink DPCCH withN_(pilot)=6 and 8 and FIG. 20D illustrates a mapping relationshipbetween the alternative frame synchronization words C₁-C₁₆ of FIG. 20Aand the shaded frame synchronization words of FIG. 20C. FIGS. 20E and20F illustrate the pilot symbol pattern of downlink DPCH with 8, 16, 32,64, 128, 256, 512, 1024, 2048 and 4096 ksps, and FIG. 20G illustrates amapping relationship between the alternative frame synchronization wordsC₁-C₁₆ of FIG. 20A and the shaded frame synchronization words of FIGS.20E and 20F. FIG. 20H illustrates the pilot symbol pattern of downlinkPCCPCH and FIG. 20I illustrates a mapping relationship between thealternative frame synchronization words C₁-C₁₆ of FIG. 20A and theshaded frame synchronization words of FIG. 20H.

Since the above is based on alternative words C₁-C₁₆, which have thesame features as the words C₁-C₈ of the first embodiment, the previousdiscussion regarding the uplink DPCCH and downlink DPCH, PCCPCH andSCCPH of the first embodiment is readily applicable. One of ordinaryskill in the art can readily appreciate the features of this embodimentbased on previous disclosure, and a detailed disclosure is omitted.

The frame synchronization words of the preferred embodiment areespecially suitable for frame synchronization confirmation. By addingthe autocorrelation functions of shaded frame synchronization words,double maximum values equal in magnitude and opposite polarity at zeroand middle shifts are obtained. This property can be used toslot-by-slot and double-check frame synchronization timing and reducethe synchronization search time. Further the present invention allows asimpler construction of the correlator circuit for a receiver, therebyreducing the complexity of the receiver. Due to various advantages ofthe present invention, the first preferred embodiment has been acceptedby the 3GPP, as shown in TS 25.211 v2.0.1, distributed June 1999, whoseentire disclosure is hereby incorporated by reference therein.

Preferred Embodiment for L=15

The above pilot patterns in accordance with preferred embodiments of thepresent invention have various advantages including framesynchronization confirmation. However, alternative pilot patterns areneeded for 15 slots (L=15) due to OHG harmonization. FIG. 21 illustratesa preferred embodiment for the new frame synchronization wordsC₁-C_(i-th), which has the auto-correlation function of lowestout-of-phase coefficient and the lowest magnitude of cross-correlationfunction with minus peak value at middle shift, where i=8. The framesynchronization words are used to design the regular pilot patterns anddiversity antenna pilot patterns of uplink DPCH, and downlink DPCH andSCCPCH of the preferred embodiment. By using the two correlationfunctions, it is possible to double check frame synchronization at zeroand middle shifts. When performance evaluation of single-check anddouble-check frame synchronization confirmation is carried out over AWGNenvironment, the words C₁-C₈ of FIG. 21 are suitable for framesynchronization confirmation

The frame synchronization words C₁-C₈ have the following two-valuedauto-correlation function:

$\begin{matrix}{{R_{i}(\tau)} = \left\{ {\begin{matrix}{15,} & {\tau = 0} \\{{- 1},} & {\tau \neq 0}\end{matrix},{i = 1},2,\Lambda,8} \right.} & (13)\end{matrix}$where R_(i)(τ) is the auto-correlation function of frame synchronizationword C_(i). Similar to L=16, the words of FIG. 21 can be divided into 4classes, as follows:E={C₁, C₂}F={C₃, C₄}G={C₅, C₆}H={C₇, C₈}The two words within the same class are PCSP. The cross-correlationspectrum for the preferred pair {C₁, C₂}, {C₃, C₄}, {C₅, C₆}, or {C₇,C₈} is

$\begin{matrix}{{R_{i,j}(\tau)} = \left\{ \begin{matrix}{{- 15},} & {\tau = 7} \\{1,} & {\tau \neq 7}\end{matrix} \right.} & (14) \\{{R_{j,i}\left( {\tau + 1} \right)} = \left\{ \begin{matrix}{{- 15},} & {\tau = 7} \\{1,} & {\tau \neq 7}\end{matrix} \right.} & (15)\end{matrix}$where R_(i,j)(τ) is cross-correlation function between two words ofpreferred pair of E, F, G, H, and i,j=1, 2, 3, . . . , 8. By combiningsuch auto-correlation and cross-correlation functions, the followingequations (16) and (17) are obtained:

$\begin{matrix}{{\sum\limits_{i = 1}^{a}{R_{i}(\tau)}} = \left\{ {\begin{matrix}{{\alpha \cdot 15},} & {\tau = 0} \\{{- \alpha},} & {\tau \neq 0}\end{matrix},{\alpha = 1},2,3,\ldots\mspace{14mu},8} \right.} & (16) \\{{\sum\limits_{i = 1}^{\alpha/2}\left( {{R_{{{2i} - 1},{2i}}(\tau)} + {R_{{2i},{{2i} - 1}}\left( {\tau + 1} \right)}} \right)} = \left\{ {\begin{matrix}{{{- \alpha} \cdot 15},} & {\tau = 7} \\{\alpha,} & {\tau \neq 7}\end{matrix},{\alpha = 2},4,6,8} \right.} & (17)\end{matrix}$

From equations (16) and (17), when α=2, FIG. 22A illustrates theaddition of two auto-correlation functions, and FIG. 22B illustrates theaddition of two cross-correlation functions between the two framesynchronization words within the same class. Similarly, from equations(16) and (17), when α=4, FIG. 22C illustrates the addition of fourauto-correlation functions, and FIG. 22D illustrates the addition offour cross-correlation functions between the four frame synchronizationwords of two classes E and F.

Since the auto-correlation function of the frame synchronization wordsC₁-C₈ in accordance with this preferred embodiment has the lowestout-of-phase coefficient, single-check frame synchronizationconfirmation is feasible by applying the positive threshold value at (a)of the auto-correlation function output of FIG. 22C. Furthermore,double-check frame synchronization confirmation is also achieved bysetting the negative threshold value at (b) of the cross-correlationfunction output of FIG. 22D.

FIG. 23A illustrates the pilot bit patterns on uplink DPCCH withN_(pilot)=2, 3, and 4, and FIG. 23C illustrates the pilot bit patternson uplink DPCCH with N_(pilot)=2,3, and 4 in accordance with analternative embodiment compared to FIG. 23A. Further, FIGS. 23E and 23Fillustrate the pilot bit patterns on uplink DPCCH with N_(pilot)=5, 6,7, and 8. The shaded parts of FIGS. 23A, 23C, 23E and 23F can be usedfor frame synchronization words, and the value of pilot bit other thanthe frame synchronization word is 1. FIGS. 23B and 23D illustrate themapping relationship between the frame synchronization words of FIG. 21,and shaded frame synchronization words of FIGS. 23A and 23D,respectively. Further, FIG. 23G illustrates the mapping relationshipbetween the frame synchronization words of FIG. 21, and the shaded framesynchronization words of FIGS. 23E and 23F.

The various description of above for uplink DPCCH when L=16 is readilyapplicable to this preferred embodiment when L=15, including thecorrelator circuits (with some modifications) and the generallycharacteristics. For example, as shown in frame synchronization wordsC₁-C₈ of FIG. 21, each word has substantially the same number of 1 and0. In this preferred embodiment, the result of b₁−b₀ is plus or minusone, e.g., close to zero. Further, when the number of slots is 15, i.e.,odd, the result of b₃−b₄ equals plus or minus one, e.g., close to zero.Further, since two frame synchronization words are used for N_(pilot)=2,3, and 4 and there are fifteen timeslots in a radio frame, the number ofpilot bits used for synchronization is 30 per frame. For N_(pilot)=5, 6,7 and 8, since four synchronization words are used for fifteen timeslotsin a radio frame, the number of pilot bits used for synchronization is60 per frame. Moreover, the result of the addition of two or fourauto-correlation functions and cross-correlation functions between twoor four frame synchronization words corresponds to FIGS. 22A-22D.

The Random Access Channel (RACH) is an uplink transport channel that isused to carry control information from the UE. The RACH may also carryshort user packets. The RACH is always received from the entire cell.FIG. 23H illustrates the structure of random access channel. The 10 msmessage is split into 15 slots, each of length T_(slot)=2560 chips. Eachslot has two parts, a data part that carries Layer 2 information and acontrol part that carries Layer 1 control information. The data andcontrol parts are transmitted in parallel.

The data part includes 10*2^(k) bits, where k=0,1,2,3. This correspondsto a spreading factor of 256, 128, 64, and 32 respectively for themessage data part. The control part has 8 known pilot bits to supportchannel estimation for coherent detection and 2 bits of rateinformation. This corresponds to a spreading factor of 256 for themessage control part. FIG. 23I illustrates the random access messagecontrol fields and there is always 8 pilot symbols per slot for channelestimation. Due to the unique characteristics of the framesynchronization words in accordance with the preferred embodiment, theframe synchronization words C₁-C₈ can be used in the pilot bit patternof the RACH for channel estimation. FIG. 23J illustrates the pilot bitpattern of the RACH, and the mapping relationship is the same as themapping relationship illustrated in FIG. 23G for N_(pilot)=8. Due to thenovel characteristics of the frame synchronization words C₁-C₈, whichcan also be used solely for channel estimation, it is easy to reuse thepilot patterns, which allows commonality between different uplinkchannels.

FIG. 24A illustrates the pilot symbol patterns on downlink DPCH whenN_(pilot)=2, 4, 8, and 16. The shaded parts of FIG. 24A can be used forframe synchronization symbols, each symbol having one framesynchronization word for the I channel branch and another framesynchronization word for the Q channel branch, and the value of pilotsymbol other than the frame synchronization word is 11. FIG. 24Billustrates the mapping relationship between the frame synchronizationwords C₁-C₈ of FIG. 21 and shaded pilot symbol patterns of FIG. 24A.

FIG. 24C illustrates the pilot symbol patterns of downlink DPCH for thediversity antenna using STTD. For the diversity pilot symbol pattern ondownlink DPCH, STTD is applied to the shaded pilot symbols #1 and #3 forN_(pilot)=8, and #1, #3, #5, and #7 for N_(pilot)=16. The non-shadedpilot symbols of #0 and #2 for N_(pilot)=8 and 0#, #2, #4 and #6 forN_(pilot)=16 are encoded to be orthogonal to the pilot symbol of FIG.24A. However, the diversity pilot pattern for downlink DPCH withN_(pilot)=4 are STTD encoded since STTD encoding requires two symbols.Since the STTD encoded pilot symbol pattern is orthogonal to ordinarypilot symbol pattern, the STTD encoded. pilot pattern can also be usedfor antenna verification of feedback mode diversity. FIG. 24Dillustrates the mapping relationship between the frame synchronizationwords C₁-C₈ of FIG. 21 and shaded pilot symbol patterns of FIG. 24C.

FIG. 25A illustrates the pilot symbol patterns for downlink SCCPCH forN_(pilot)=8 and 16, and FIG. 25B illustrates the mapping relationship ofthe frame synchronization words C₁-C₈ of FIG. 21 and shaded pilot symbolpatterns of FIG. 25A. Further, FIG. 25C illustrates the pilot symbolpatterns of downlink SCCPCH for N_(pilot)=8 and 16 for the diversityantenna using STTD, and FIG. 25D illustrates the mapping relationshipbetween the frame synchronization words C₁-C₈ of FIG. 21 and shadedpilot symbol patterns of FIG. 25C.

As can be appreciated, the various description of above for downlinkDPCH when L=16 is readily applicable to this preferred embodiment whenL=15, including the correlator circuits (with some modifications) andthe generally characteristics. Moreover, the result of the addition oftwo or four auto-correlation functions and cross-correlation functionsbetween two or four frame synchronization words corresponds to FIGS.22A-22D.

In order to evaluate the performance of the frame synchronization wordsin accordance with the preferred embodiment for 15 slots per frame, thefollowing events and parameters are first defined:

-   H₁: The event that the auto-correlator output exceeds the    predetermined threshold at zero slot offset.-   H₂: The event that the auto-correlator output exceeds the    predetermined-threshold at zero slot offset or the cross-correlator    output is smaller than −1×(predetermined threshold) at 7 slot    offset.-   H₃: The event that the auto-correlator exceeds the predetermined    threshold at slot offset except zero.-   H₄: The event that the cross-correlator output is smaller than    −1×(predetermined threshold) at slot offset except 7.-   P_(S): Probability of a frame synchronization confirmation success.-   P_(FA): Probability of a false alarm.

The frame synchronization is confirmed if the output of the correlatorusing the frame synchronization word exceeds the predeterminedthreshold. The success of the frame synchronization confirmation isdetermined when the successive S_(R) frame synchronization is confirmed.Otherwise, the frame synchronization confirmation failure is determined.Thus, the probability of a frame synchronization confirmation success isdefined by

$\begin{matrix}{P_{S} = \left\{ \begin{matrix}{\left( {{Prob}\left( H_{1} \right)} \right)^{S_{R}},} & {{single}\mspace{14mu}{check}} \\{\left( {{Prob}\left( H_{2} \right)} \right)^{S_{R}},} & {{double}\mspace{14mu}{check}}\end{matrix} \right.} & (18)\end{matrix}$The probability of a false alarm can be expressed as

$\begin{matrix}\begin{matrix}{P_{FA} = {{Prob}\left( H_{3} \right)}} \\{= {{Prob}\left( H_{4} \right)}}\end{matrix} & (19)\end{matrix}$

The parameters of FIG. 26A are used to evaluate the performance of thepilot bit pattern on uplink DPCCH over AWGN. FIG. 26B illustrates theprobability of frame synchronization confirmation success P_(S) onuplink DPCCH with N_(pilot)=6 over AWGN channel. Further, FIG. 26Cillustrates the probability of a false alarm P_(FA) on uplink DPCCH withN_(pilot)=6 over AWGN channel. The P_(S) and P_(FA) are given as afunction of E_(b)/N₀ ratio (E_(b)=energy per bit, N₀=noise powerspectral density).

The P_(S) of single-check and double-check frame synchronizationconfirmation with S_(R)=3 on uplink DPCCH is smaller than 0.945 and 0.99at −5 dB, respectively. Further, about 4 dB gain is obtained byemploying double-check method compared to single-check method. From FIG.26C, the probability of a false alarm with normalized threshold=0.6 at−5 dB is smaller than 2.5×10⁻⁴. The pilot pattern can be used for framesynchronization confirmation since perfect frame synchronizationconfirmation success with zero false alarm was detected at Eb/No=0 dBwhen double-check frame synchronization confirmation method was used.

FIG. 27 is a comparision chart between the embodiments for 15 timeslotsand 16 slots. Including the various advantages for L=16, the pilotbit/symbol patterns for L=15 in accordance with the preferred embodimenthave additional advantages. By using this property/characteristics ofthe frame synchronization words, double-check frame synchronizationscheme can be obtained. There is significant gain about 4 dB byemploying the double-check frame synchronization confirmation methodcompared to single-check method. However, in the case of 15 slots, thecomplexity of the correlator circuit is doubled since an auto-correlatorfor positive peak detection and a cross-correlator for negative peakdetection are used.

Since the auto-correlation function of the frame synchronization wordsof the 15 slots has the lowest out-of-phase coefficient, thesingle-check frame synchronization confirmation method can also beemployed; whereas, in the case of 16 slots, there is some problems dueto +4 or −4 out-of-phase coefficients. The pilot patterns of 15 slots isvery suitable for frame synchronization confirmation since perfect framesynchronization confirmation success with zero false alarm was detectedat Eb/No=0 dB on uplink DPCH when double-check frame synchronizationconfirmation method was used. Due to the various advantageous of thepreferred embodiment, the pilot bit/symbol patterns of 15 slots havebeen again accepted by the 3GPP.

The foregoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teaching can bereadily applied to other types of apparatuses. The description of thepresent invention is intended to be illustrative, and not to limit thescope of the claims. Many alternatives, modifications, and variationswill be apparent to those skilled in the art. In the claims,means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method of confirming frame synchronization in a communicationchannel between a base station and a mobile station: (a) generatingcontrol signals and data signals within the communication channel, saidcontrol signals having a first sequence of L-bits and a second sequenceof L-bits; (b) autocorrelating the first and second sequences togenerate first and second autocorrelated values; (c) cross-correlatingthe first and second sequences to generate fist and secondcross-correlated values; and (d) combining the first and secondautocorrelated values and the first and second cross-correlated values.2. The method of claim 1, wherein lowest out-of-phase coefficients ofthe autocorrelation function is −4.
 3. The method of claim 1, wherein aresult of step (d) comprise maximum peaks at zero and middle timeshifts, which are equal to each other and opposite in polarity.
 4. Themethod of claim 1, wherein the communication channel includes a framehaving L number of slots, wherein step (d) allows at least one ofslot-by-slot frame synchronization, channel estimation, double checkframe synchronization and single frame synchronization.
 5. The method ofclaim 1, wherein each of said first and second sequences of L-bitsincludes a first prescribed number (b₀) of bit values equal to “0 ” anda second prescribed number (b₁) of bit values equal to “1”, whereinb₁−b₀ is +1 or −1.
 6. The method of claim 1, wherein the communicationchannel comprises a plurality of frames, each frame having L number ofslots and each slot has N number of pilot bits such that there are Nnumber of sequences of L-bits in a frame, said first and secondsequences being sequences of the N number of sequences.
 7. The method ofclaim 3, wherein the maximum peak at zero time shift is a firstprescribed number*L, and the maximum peak at middle time shift is—(prescribed number*L).
 8. The method of claim 6, wherein betweenadjacent sequences, there are a prescribed number b₃ of bit values whichare the same and there a prescribed number b₄ of bit values which aredifferent such that b₃-b₄ is +1 or −1.
 9. The method of claim 6, whereinsaid control signals include a third sequence of L-bits and a fourthsequence of L-bits, and further comprising the steps of: autocorrelatingthe third and fourth sequences to generate third and fourthautocorrelated values; and cross-correlating the third and fourthsequences to generate third and fourth cross-correlated values, whereinthe combining step comprises combining the first, second, third andfourth autocorrelated values and the first, second, third and fourthcross-correlated values.
 10. The method of claim 9, wherein thesequences used for frame synchronization are members of a family of isequences.
 11. The method of claim 10, wherein i=8, L=15 and N=2 to 32,each frame having a period of 10 ms and each slot having a period ofabout 0.667 ms.
 12. The method of claim 9, wherein step (d) comprisesadding the first, second, third and fourth autocorrelated values andadding the first, second, third and fourth cross-correlated values. 13.A method of confirming frame synchronization: generating a plurality offrame words, each frame word having a plurality of bits; performingautocorrelation functions on a pair of frame words to generate a pair ofautocorrelated value sets; performing cross-correlation function on apair of frame words to generate a pair of cross-correlated value sets;and combining the pair of autocorrelated value set and cross-correlatedvalue sets such that two peak values equal in magnitude and opposite inpolarity are achieved at zero and middle time shifts.
 14. A method ofgenerating pilot signals of a prescribed pattern within a frame having15 slots: generating N pilot bits for each slot; and forming N words of15-bit based on above generating step, wherein each of a prescribednumber of N words has a first prescribed number b0 of bit values of “0 ”and a second prescribed number b₁ of bit values of “1 ”, such that b₁-b₀is +1 or −1.